1. Field of the Invention
The present invention relates to an improvement in or relating to a pipe washing apparatus for use in cleaning for instance, drain ducts, which pipe washing apparatus is capable of running forward and circumferentially in the pipe while scrubbing and washing away the scales thus removed.
2. Description of Related Art
A conventional pipe washing apparatus is disclosed in Japanese Patent 4-200781(A). As shown in FIG. 6, it comprises a nozzle support 1 fixed to the end of a washing hose H, which is to be inserted in a pipe B to be washed inside, a nozzle 2 attached to the nozzle support 1 and a slender nozzle guide member 3 extending from the nozzle 2. The nozzle 2 has a first radial water-jet throttle 2a directed radially to the inner circumference of the pipe B. The nozzle support 1 has second oblique water jet throttles 1c directed obliquely backward for driving the pipe washing apparatus forward.
Japanese Patent 2-207879(A) shows another pipe washing apparatus. As shown in FIG. 7, it comprises a nozzle support 1 fixed to the end of a washing hose H, which is to be inserted in a pipe B to be washed inside, a nozzle 2 rotatably attached to the nozzle support 1 and a slender nozzle guide member 3 extending from the nozzle 2 forward. The nozzle support 1 has orifices (second water jet throttles) 1c. The nozzle 2 has a radial water-jet throttle (first water-jet throttle) 2a. The orifice 1c of the nozzle support 1 is smaller than the water-jet throttle 2a of the nozzle 2. The slender nozzle guide member 3 extends aside from the center axis of the longitudinal channel of the nozzle 2.
As for the pipe washing apparatus shown in Japanese Patent 4-200781(A) the nozzle 2 is fixed to the cylindrical end 1d of the nozzle support 1 via an associated bearing 6, and the guide member 3, which is composed of a slender stem 3a having a ball 3b fixed to its end, is fixed to one side of the nozzle 2. The massive spherical end 3b of the slender stem 3a is put aside from the center of rotation about which the nozzle 2 is rotated. This cantilever-like support structure is disadvantageous to the rotating of the nozzle 2 while jetting water to the inner circumference of the pipe B for scraping; such cantilever-like support structure burdens undue load on the nozzle shaft 2e , causing an increased bending moment to be applied to the nozzle shaft 2e. This is the main cause for the significant wearing or breaking of the nozzle assembly.
As for the pipe washing apparatus shown in Japanese Patent 2-207879(A) this has a similar cantilever-like support structure to hold a nozzle guide member, the stem of which is even longer than the nozzle guide member in the pipe washing apparatus shown in Japanese Patent 4-200781(A). To assure that undesired vibration caused by the rotating nozzle guide 3 is prevented the bearing 6 of the nozzle shaft must be mounted deep in the hollow nozzle support 1. Thus, extra manufacturing cost is involved.